This invention relates to a new and improved method and apparatus which eliminates offensive and toxic particulate and gaseous contaminants, such as smoke, grease, volatile organic compounds, carbon monoxide and other toxic gases, from an exhaust flow, and recirculating the cleaned and benign exhaust flow back into a confined environment from which the exhaust originated. In addition to avoiding the discharge of undesirable and potentially harmful contaminants into the ambient environment, recirculating the cleaned and benign exhaust flow saves a substantial portion of the thermal energy of the air from the exhaust flow that would otherwise be lost by discharging the exhaust flow into the ambient environment. Thus, the present invention substantially reduces the cost of heating, cooling or otherwise conditioning makeup air to replace the conditioned air which is normally lost in an exhaust flow discharged into the ambient environment.
Modern environmental concerns and regulations impose significant requirements for removing contaminants and undesirable constituents from the exhaust flow discharged into the ambient environment from industrial and other commercial operations. In some cases, the discharged exhaust flow must be cleaned or otherwise conditioned before it may it is discharged. For example, food preparation establishments are now required, or will soon be required, to remove the relatively high concentrations of smoke and fat airborne contaminants from the cooking exhaust. Not only is smoke generated while cooking the food, but particulate matter such as grease and fat and volatile contaminants such as odor are also created. Moreover, the hydrocarbon fuels which are burned while cooking the food generate carbon monoxide, which is toxic and may be lethal in concentrated doses. Other examples of business and industrial operations which generate exhaust with offensive and toxic particulate and gaseous contaminants are automobile repair shops, clothes drycleaning operations, and waste and water treatment plants.
Industrial and business operations frequently discharge the exhaust flow from the confined interior environment of the establishment into the ambient environment outside of the establishment. Usually the exhaust consists not only of the smoke, odor, particulates, volatile organic compounds, carbon monoxide and other toxic gases, but also air drawn from within the confined environment of the establishment which is used to carry these contaminants outside of the establishment and into the ambient environment. Some types of these industrial and business operations, such as restaurants or food preparation establishments, generate a relatively large amount of such contaminants, and the amount of air consumed from within the confined environment to exhaust the contaminants is substantial. Makeup air must be admitted into the confined environment of the establishment to replace the air consumed by the exhaust flow.
The amount of makeup air required to replace the air of the exhaust flow is usually a significant portion of the overall air required to condition the interior confined environment of the establishment. Because the interior air used in the exhaust flow is drawn from the heated, cooled or otherwise conditioned air or within the interior confined environment, the makeup air admitted into the confined environment to replace the exhaust air flow must also be heated, cooled or otherwise conditioned. Otherwise, the desired thermal environment within the establishment could not be maintained. Of course, the thermal energy content of the air within the exhaust flow is when the exhaust flow is discharged into the ambient environment.
The energy required to heat, cool or otherwise condition makeup air may be a significant operating cost of the establishment. For example, the size and energy consumption of the heating and cooling equipment required to condition the makeup air for a small fast food restaurant is approximately four times the size and capacity that would be otherwise required if air was not withdrawn from within the interior of the confined environment as part of the cooking exhaust flow into the ambient environment. Considerable expense is involved in obtaining the increased capacity of the heating and cooling equipment for conditioning the makeup air, and in operating that equipment.
One of the significant drawbacks to recirculating the exhaust air from confined environments such as food preparation establishments, has been an inability to clean the contaminants from the exhaust air in a cost-efficient manner. The previous invention referenced above offers a relatively low cost and highly effective solution of ridding the exhaust air of particulate and gaseous contaminants, thus offering the possibility of recirculating the cleaned and benign exhaust flow back into the confined environment.
It is with respect to these and other considerations that the present invention has evolved.
One primary improvement available from the present invention is an improved cability to remove offensive and harmful particulate and gaseous contaminants from an exhaust flow, and to convert toxic gaseous components of the exhaust flow into neutralized or benign non-toxic components, thereby allowing the cleaned and neutralized exhaust flow to be recirculated back into a confined environment of a commercial or industrial establishment. Another improvement relates to recirculating a significant portion of the cleaned and benign exhaust flow to avoid losing the energy content of the conditioned air which is part of the exhaust flow. Another improvement relates to reducing the capacity of the heating, cooling and air conditioning equipment and the cost of operating that equipment to condition makeup air to compensate for the air consumed by the exhaust flow. The operating costs of a food preparation establishment, or any other type of industrial or commercial establishment may be substantially reduced.
These and other improvements are achieved in a recirculation system for retaining substantial thermal energy content of air drawn from within a confined environment in which offensive and toxic particulate and gaseous constituents are generated as exhaust contaminants. The recirculation system includes a collector device located within the confined environment to receive and establish a flow of the exhaust contaminants and air from within the confined environment, and a cleaner device connected to receive the flow of the exhaust contaminants and air from the exhaust collector device. The cleaner comprises a scrubber module, a liquid removal module and a filtering and conversion module connected in series through which the exhaust flow passes. The scrubber module may include flow passageways through which the flow of exhaust contaminants and air passes and into which cleaning liquid is distributed for mixture with and entrainment of the particulate contaminants of the flow. The liquid removal module removes the cleaning liquid from the flow from the scrubber module. The filtering and conversion module includes an odor-removing filter for removing odor from the exhaust flow from the liquid removal module, and the filtering and conversion module also includes a catalyst which facilitates conversion of toxic gases in the exhaust flow from the liquid removal module into benign gases, such as the conversion of carbon monoxide into carbon dioxide. A delivery device is located within the confined environment to receive the cleaned and neutralized flow from the cleaner device and to discharge the flow into the confined environment.
Other useful aspects of the recirculation system include an exhaust collection hood located over the source of the exhaust and into which the cleaned and benign flow from the cleaner may be discharged. It is also useful for the catalyst to operate at room temperature to oxidize the toxic gases into benign gases, by using air from the exhaust flow. A heater may periodically heat the catalyst to a predetermined temperature sufficient to regenerate the catalytic characteristics of the catalyst. A catalyst cell of the filtering and conversion module may include a layer of particles of the catalyst and a layer of carbon particles, and the heater may be positioned within the layer of catalyst particles. The filtering and conversion module may further comprise a filter device such as a HEPA, DOP or BAG filter, connected to receive the flow from the liquid removal device. The scrubber module may include a baffle-defining structure comprising a plurality of vertically spaced and interdigitated deflection plates which define a serpentine-shaped flow passageway through which the flow of the exhaust contaminants and the air move, and one or more liquid distributors positioned within each passageway to flow liquid cleaning agent into the exhaust flow. The liquid removal device may comprise a curved sidewall structure along which the flow moves in a curved motion to force liquid remaining in the flow from the scrubber module to coalesce into liquid and drain along the sidewall structure, and to cause contaminants in the flow to be forced against the sidewall structure and become entrained in the liquid.
The above noted and other improvements are also achieved by a method of recirculating air to retain substantial thermal energy content of the air drawn from within a confined environment of an establishment which generates offensive and harmful particulate and gaseous constituents as exhaust contaminants. The method includes establishing a flow of the exhaust contaminants and air from within the confined environment, liquid scrubbing contaminants from the flow, moving the flow after liquid scrubbing in a curved path to force liquid mist to coalesce into liquid by centrifugal force caused by moving the flow in the curved path, removing the coalesced liquid from the flow, removing odor from the flow after the coalesced liquid has been removed, catalyzing toxic gases remaining in the flow into benign gases after the coalesced liquid has been removed, and discharging the cleaned and neutralized flow into the confined environment.
Other useful aspects of the method include catalyzing toxic gases into benign gases at approximately room temperature, and periodically heating the catalyst to a predetermined temperature greater than room temperature to regenerate the catalytic characteristics of the catalyst. Still other useful aspects involve collecting the air and exhaust contaminants from within the confined environment in an exhaust collection hood and discharging the cleaned and neutralized exhaust flow into the confined environment within the hood.
A more complete appreciation of the present invention and its scope, and the manner in which it achieves the above noted improvements, can be obtained by reference to the following detailed description of presently preferred embodiments of the invention taken in connection with the accompanying drawings, which are briefly summarized below, and the appended claims.